Conventional isotonic or displacement type of hand controllers such as joysticks and yokes rely on a cumbersome kinematic mechanism to restrict a human operator's three dimensional movements into a confined space. Mechanical linkages such as shafts, gears, bearings and springs, etc. are employed as necessary to transfer motions from the human operator to the electronic sensors attached to the mechanism. Widely used sensors such as potentiometers, transformers, Hall effect sensors, magneto-resistive sensors, optical and magnetic encoders, etc. can measure movement only along a single axis. Control devices employing these sensors make indirect measurements of the operator's movements and impose limitations on the design of a human machine interface (HMI). In order to provide a controller with capability in more than two DOFs (degrees of freedom), a conventional approach is to connect or stack several single- or two-axis mechanisms together. Controllers constructed according to this approach are complex to implement and awkward to use. In addition, using such a controller is not intuitive for the user; this lengthens the user's learning curve.
Due to inherent kinematic requirements, the mounting location and alignment of the sensors in such devices are often restricted, for example, to be at or near a pivot axis. Design flexibility and configurability are therefore limited.
Conventional control devices are often installed permanently to a fixed platform due to the size and weight of the kinematic mechanism. It is cumbersome to remove such equipment. In addition, when a conventional control device is mounted in a moving vehicle, the motion sensors therein may be susceptible to fictitious forces. Furthermore, these devices generally contain moving components that are subject to friction, backlash, binding, and deterioration over time and under changing environmental conditions, which thus impact their long-term reliability. Their size and weight often make such devices not suitable for portable or wearable applications.